Direct measures of laryngeal muscle force have been made by techniques involving acute experiments which cannot be applied to man. In recent years, the measurement of intramuscular fluid pressures (IMFPs) during muscle contraction, pioneered by A.V. Hill, has provided an alternative non-destructive technique for the quantification of muscle mechanical output, which is applicable in any laryngeal muscle. In isometric conditions the measure correlates more closely to the time course of muscle contraction than does the electromyogram, and this relation is stable in situations in which the relation of electromyography to force varies, such as fatigue and high effort levels. Our pilot research has studies the relation of canine thyroarytenoid muscle IMFPs to force and EMG in isometric contraction. The proposed research will extend this technique to the posterior cricoarytenoid (PCA) muscle, the subject of much clinical laryngological research, also in dogs. The first stage of research will involve refining the application of the technique in PCA, mapping variation of IMFPs within the muscle in order to make cross-subject comparisons,and establishing the relations between IMFPs measured with two different systems, each of which has important advantages. The second stage will examine the relations between force and IMFPs in these muscles, in isometric conditions and with muscle length change. The third stage will compare observations of PCA activity with observations of the same muscle in controlled experiments of the type studied in Stage 2. The result of these three stages will be to prepare the way for measurement of these quantities in the human larynx. With the ongoing further miniaturization of transducers, this technique can be developed into a research and diagnostic tool, which will e.g. provide a tool for clinical assessment of laryngeal muscle strength after laryngeal nerve damage, or make it possible to monitor the alteration of muscle strength after (experimental) surgery.